Corrosion inhibition of pure aluminium and AA2014‐T6 alloy by strontium chromate at low concentration

Abstract

The influence of a low concentration of strontium chromate on the corrosion inhibition of superpure aluminium and AA2014-T6 aluminium alloy in 0.6 M chloride solution has been investigated to simulate the leaching process of inhibitors from coatings. The potential-time and polarisation behaviour show influences on both the anodic and cathodic kinetics on the superpure aluminium surface. However, predominant cathodic inhibition was observed for the AA2014-T6 aluminium alloy. It was evident that chromium species were reduced at cathodic second phase particles, forming a thin passive film at the cathodic sites, which blocks the oxygen reduction reaction and, consequently, provides effective corrosion inhibition.

Role of Strontium on Sensitization and Unusual Passivation Behavior of a 5xxx Series Aluminum Alloy Containing a Trace Amount of Chromium

“…Cr 6+ reduces the oxygen reduction reaction and also acts as a film-forming agent. 28,29 Since Sr 2+ , Cr 6+ , and Cr 3+ are found in the passive film, there is a possibility that the passive film contains strontium chromate (SrCrO 4 ) which is a very strong passivator. This oxide is sparingly soluble in water and thus can offer good protection to the underlying metal.…”

“…This suggestion gains credence from the fact that SrO.CrO 3 is one of the most effective and valuable pigments usually used in paints, primers, and specialty coatings to improve the performance of the paints. 28,29 Sr may stabilize hexavalent chromium, which is a better inhibitor than trivalent chromium. More studies are needed to understand the synergy between Cr and Sr in improving the passivation of the aluminum alloy.…”